MYCN and neuroblastoma: To determine whether increased c-MYC in PD cell lines might be due to the selective pressure of 13-cisRA treatment, the SMS-LHN (LHN) human neuroblastoma cell line (MYCN expression without genomic amplification)17 was treated with 13-cisRA, mimicking the clinical drug exposures obtained in children with neuroblastoma (5 μM for 2 wks of every 4 wks for 6 cycles).